Novel Trigger-Capable Modules for the Future CMS Tracking Detector and Inclusive Top Quark Pair Production Cross Section at $\sqrt{s} = 13$ TeV

This work covers two important aspects in the field of high-energy physics; detector development and physics data analysis. The first part of this thesis is devoted to the detector development activities for the Phase-II upgrade of the Compact Muon Solenoid (CMS) experiment’s outer tracking detector. To cope with the increased luminosity during the high-luminosity era of the Large Hadron Collider (LHC), it is foreseen to replace the existing tracking system of CMS with an entirely new system. Owing to a novel module concept called the $p_T$–module, the upgraded tracking system will be able to provide first level trigger information by means of an on-board momentum discrimination logic. This will be achieved using a new readout chip, the so-called CMS Binary Chip (CBC). The very first test beam measurement using $p_T$ –module prototypes, equipped with the CBC chip is presented and discussed. The obtained results serve as a proof-of-concept for such modules and shows that the CBC performs as expected. In the second part of this thesis, the measurement of the top quark pair production cross section is addressed. The measurement is performed using $2.2 fb^{−1}$ of data collected by the CMS detector at a center-of-mass energy of 13 TeV. Results are shown in the $e\mu$ di-lepton channel, and for the first time at such energy, in the $ee$ and $\mu\mu$ channels. With an improved treatment of systematic uncertainties, the results in all three channels are found to be in agreement with the theoretical predictions.